i s o i s o

Illinois Science OlympiadIllinois Science Olympiad

Coaches Meeting 2011:Coaches Meeting 2011:Materials Science Materials Science

WisconsinWisconsinScienceScienceOlympiadOlympiad

New Rules -New Rules - Materials Performance and Nano Materials Performance and Nano focusfocus

Structure and Performance Relationships

Students will perform laboratory based experiments Students will perform laboratory based experiments designed to evaluate the relationship between the designed to evaluate the relationship between the atomic/molecular structure and the performance atomic/molecular structure and the performance characteristics of common materials. characteristics of common materials.

Structure and Characteristics of: metals, ceramics, Structure and Characteristics of: metals, ceramics, polymers, semi-conductors and composites. - Utilizing polymers, semi-conductors and composites. - Utilizing stress-strain curves to evaluate the Young’s modulus.stress-strain curves to evaluate the Young’s modulus.

Nanomaterials - focus on nanoparticles and carbon focus on nanoparticles and carbon nanotubes. nanotubes.

General introductory topics regarding the physical General introductory topics regarding the physical and chemical properties that arise within the nano and chemical properties that arise within the nano size regime. size regime.

surface area to volume ratiossurface area to volume ratiosquantum effectsquantum effectsnanomaterials visualization. nanomaterials visualization.

Understand SEM, TEM, AFM micrographs Understand SEM, TEM, AFM micrographs scalingscaling

Cubic crystal structures. Cubic crystal structures. Formula, density, dimensions. Miller Indices, and Formula, density, dimensions. Miller Indices, and use of x-ray data to determine unit cell use of x-ray data to determine unit cell dimensions. Internet based modeling and/or dimensions. Internet based modeling and/or simulations may be incorporated into event tasks simulations may be incorporated into event tasks and questions. and questions.

Materials CharacteristicsMaterials Characteristics

ρ ≡ Densityρ ≡ Density

Materials CharacteristicsMaterials CharacteristicsMetals: low electronegativity metal cationic atoms in a “sea” of Metals: low electronegativity metal cationic atoms in a “sea” of delocalized electrons. Metallic bonds from electrostatic delocalized electrons. Metallic bonds from electrostatic interaction - different from ionic bonds. interaction - different from ionic bonds. Conducts electrons on the delocalaized valence level “sea” of Conducts electrons on the delocalaized valence level “sea” of electronselectrons

malleable/ductile, hard, tough, can be brittle.malleable/ductile, hard, tough, can be brittle.

IronIron

CeramicCeramicss covalent and ionic bonding of inorganic non-metals. electrons are covalent and ionic bonding of inorganic non-metals. electrons are

localized in bonds - poor conductors, brittle and very thermally localized in bonds - poor conductors, brittle and very thermally stable.stable.

The crystal structure of bulk ceramic compounds is determined by The crystal structure of bulk ceramic compounds is determined by the amount and type of bonds. The percentage of ionic bonds can the amount and type of bonds. The percentage of ionic bonds can be estimated by using electronegativity determinations. Resistance be estimated by using electronegativity determinations. Resistance to shear and high-energy slip is extremely high.to shear and high-energy slip is extremely high.

Atoms are bonded more strongly than metals: fewer ways for atoms Atoms are bonded more strongly than metals: fewer ways for atoms to move or slip in relation to each other. Ductility of ceramic to move or slip in relation to each other. Ductility of ceramic compounds is very low and are brittle. Fracture stresses that initiate compounds is very low and are brittle. Fracture stresses that initiate a crack build up before there is any plastic deformation and, once a crack build up before there is any plastic deformation and, once started, a crack will grow spontaneously.started, a crack will grow spontaneously.

http://mst-online.nsu.edu/mst/ceramics/ceramics3.htm

Alumina Alumina AlAl22OO33

Semi-conductorsSemi-conductorsMetalloid in composition (w/ exception). Covalently bonded. Metalloid in composition (w/ exception). Covalently bonded. More elastic than ceramics. More elastic than ceramics.

characterized by the presence of a band gap where characterized by the presence of a band gap where electrons can become delocalized within the framework. electrons can become delocalized within the framework.

PolymersPolymers macromolecules containing carbon covalently macromolecules containing carbon covalently bonded with itself and with elements of low bonded with itself and with elements of low atomic numberatomic number

molecular chains have long linear structures molecular chains have long linear structures and are held together through (weak) and are held together through (weak) intermolecular (van der Waals) bonds. Low intermolecular (van der Waals) bonds. Low melting temp. melting temp.

Materials Performance Materials Performance

Optical properties Optical properties (Quantum Dots, LEDs)(Quantum Dots, LEDs)

Magnetic properties Magnetic properties (ferrofluids)(ferrofluids)

Electronic Properties Electronic Properties ( semiconductors)( semiconductors)

Thermal and Mechanical Properities Thermal and Mechanical Properities (plastics, metals, (plastics, metals,

ceramics)ceramics)

Mechanical PerformanceMechanical Performance

Stress Vs. Strain Stress Vs. Strain relationshiprelationship

http://www.yourbuilding.org/Article/NewsDetail.aspx?p=83&id=1570

Linear Deformation - Linear Deformation - Stress and Stress and StrainStrain

StressStress - - force force applied over a given applied over a given area. Units of lbs/inarea. Units of lbs/in22 or Gigapascalsor Gigapascals

StrainStrain - - Deformation Deformation of material as a of material as a change in dimension change in dimension from initial. *Unitlessfrom initial. *Unitless

Stress, Strain, and Young’s Stress, Strain, and Young’s ModulusModulus

Young’s ModulusYoung’s Modulus- a measure of - a measure of material “stiffness”material “stiffness”- - EE = = σ/εσ/ε

= F/A = F/A l/Ll/L

Hooke’s Law: Hooke’s Law: F = F = kk∗∗ΔΔx spring constant: x spring constant: k = F/k = F/ΔΔxx

True elastic behavior vs. True elastic behavior vs. elastic regionelastic region

GlassGlassRubberRubber

Vable, M. Mechanics of Materials: Mechanical properties of Materials. Sept. Vable, M. Mechanics of Materials: Mechanical properties of Materials. Sept. 2011 2011

Relationship of Relationship of EE and materials and materials characteristics:characteristics: Polymers Polymers

http://www.nrc-cnrc.gc.ca/eng/ibp/irc/cbd/building-digest-157.html

m = m = EE

EE, Young’s , Young’s ModulusModulus GPaGPa psipsi

RubberRubber 0.01-0.10.01-0.1 1500-150001500-15000

TeflonTeflon 0.50.5 75,00075,000

NylonNylon 2 - 42 - 4 290,000-290,000-580,000580,000

AluminumAluminum 6969 10,000,00010,000,000

*Glass*Glass 50 - 9050 - 90 n/an/a

CopperCopper 117117 17,000,00017,000,000

SteelSteel 200200 29,000,00029,000,000

DiamondDiamond 12201220 150 -175 million150 -175 million

Example Example QuestionQuestion

The deflection d of the mid-point of a centrally The deflection d of the mid-point of a centrally loaded simple beam of uniform rectangular loaded simple beam of uniform rectangular cross section is given byd = (Wlcross section is given byd = (Wl33)/(4ab)/(4ab33Y) For a Y) For a circular beam of radius r the expression circular beam of radius r the expression becomesd = (Wlbecomesd = (Wl33)/(12πr)/(12πr44Y) Y) where Y is the Young’s Moduluswhere Y is the Young’s Modulus

A different application of Young’s A different application of Young’s ModulusModulus

http://blog.cencophysics.com/2009/08/beam-deflection-youngs-modulus/

NanomaterialsNanomaterials - - NanoworldNanoworld

The size regime of the The size regime of the nanoworld is 1 million nanoworld is 1 million times smaller than a times smaller than a millimeter.millimeter.

SEM, TEM, AFM Images of SEM, TEM, AFM Images of CdSe Quantum DotsCdSe Quantum Dots

Picture: C.P. Garcia, V. Pellegrini , NEST (INFM), Pisa. Artwork: Lucia Covihttp://mrsec.wisc.edu/Edetc/SlideShow/slides/quantum_dot/QDCdSe.htmlhttp://www.jpk.com/quantum-dots-manipulation.207.en.html?image=adf24cc03b304a4df5c2ff5b4f70f4e9

200 nm200 nm

Surface area to volume Surface area to volume ratioratio

VolumeVolume Surface AreaSurface Area

Consequences of Large Consequences of Large Surface Area to Volume ratioSurface Area to Volume ratio

Gas law: P = nRTGas law: P = nRTVV

As volume decreases, SA As volume decreases, SA increases as does pressureincreases as does pressure

Electron conducting & band Electron conducting & band gapsgaps-- Conducting is flow Conducting is flow of e- from VB of e- from VB through the C.B.through the C.B.* In metals, CB is * In metals, CB is linked to VB directlylinked to VB directly

- Semiconductors - Semiconductors require some energy require some energy input to overcome a input to overcome a gap between VB and gap between VB and CBCB

- Insulators have a band gap too large to overcome, - Insulators have a band gap too large to overcome, thus they insulate against e- conduction.thus they insulate against e- conduction.

Characteristics of Characteristics of LightLight

Wave-like properties:Wavelength (λ) or Frequency (ν)c = λν (c is the speed of light, 3.0x108

m/s)

Particle-like properties:A photon is a packet of energy (E)E = hν = h c/ λ (h= 6.6 x 10-34 J s)E = 2.0x10-25/ λ (hc= 2.0 x 10-25 J m)

Band gap, quantum effects, Band gap, quantum effects, colorcolor

As size decreases, the As size decreases, the electrons of the electrons of the nanoparticle become nanoparticle become confined to a smaller confined to a smaller space, and the band gap space, and the band gap increasesincreases

Calculate particle size based on Calculate particle size based on UV-Vis spectroscopy - Particle in UV-Vis spectroscopy - Particle in a Boxa Box

http://www.beilstein-journals.org/bjnano/single/articleFullText.htm?publicId=2190-4286-1-14#E1

CdSe Quantum dots, CdSe Quantum dots, 1.5 - 2 nm in size1.5 - 2 nm in size

Crystal Crystal StructureStructure

The size and shape of a unit cell is described, in three dimensions, by the lengths of the three edges (a, b, and c) and the angles between the edges (α, β, and γ).

These quantities are referred to as the lattice parameters of the unit cell.

*Only Po has this structure*Only Po has this structure

Simple Simple CubicCubic

Example QuestionsExample Questions

Characterizing a CrystalCharacterizing a Crystal

Interference in Scattered Waves

X-ray Diffraction in Crystalline SolidsX-ray Diffraction in Crystalline Solids

Diffraction PatternsDiffraction Patterns

X-Ray powder X-Ray powder diffraction diffraction patternspatterns

Miller Indices Miller Indices - Understanding crystal orientation- Understanding crystal orientation

http://www.doitpoms.ac.uk/tlplib/miller_indices/printall.php

Additional Great ResourcesAdditional Great Resourceswww.nano.govwww.mrsec.wiwww.mrsec.wisc.edu/nanohttp://www.terrificscience.org/lessonpdfs/PolymerLab06.pdfhttp://phet.colorado.edu/en/simulation/photoelectrichttp://phet.colorado.edu/en/simulation/shttp://phet.colorado.edu/en/simulation/semiconductorhttp://phet.colorado.edu/en/simulation/conductivityhttp://phet.colorado.edu/en/simulation/whttp://phet.colorado.edu/en/simulation/wave-interference